In a wireless communications system, a large-scale antenna array can bring space domain multiplexing gains, so as to improve communication throughput of the wireless system. Therefore, large-scale antenna arrays are considered as a key technology of future wireless communications systems. However, in order to obtain the space domain multiplexing gains brought by multiple antennas, a base station in the wireless system needs to learn channel state information (CSI) of a channel between a transmitting antenna of a base station to a receiving antenna of a user equipment (UE) device. CSI represents information about channel attenuation from the base station to the UE, and is fed back, after being measured and calculated by the UE, to the base station by using an uplink feedback link.
As a quantity of antennas in a large-scale antenna array increases, an amount of information about CSI that is feedback from the UE to the base station greatly increases, so that a large number of feedback overheads are brought to the entire wireless communications system. The large number of feedback overheads offset a benefit of a diversity gain brought by the large-scale antenna array, and reduce actually effective frequency spectrum utilization. In another aspect, a limited feedback method is generally used in an actual wireless communications system, that is, a feedback capacity of an uplink feedback link is given. As an amount of CSI information that needs to be fed back continuously increases, a quantity of bits that can be assigned for each piece of CSI gradually decreases; then, quality of CSI fed back to the base station from the UE gradually decreases. Therefore, CSI feedback efficiency needs to be improved, so as to ensure the quality of CSI fed back to the base station and improve spectrum utilization of the wireless communications systems.
A conventional CSI feedback method of an existing wireless communications system includes: UE uses pilots sent by a base station to measure and calculate a CSI parameter corresponding to a subcarrier, and the UE quantizes the entire CSI parameter by using a codebook; afterwards, the quantized CSI parameter is fed back to the base station through an uplink from the UE to the base station, and the base station figures out the corresponding CSI parameter by using the same codebook.
Therefore, in the existing CSI feedback manner, characteristics of CSI in a large-scale antenna array are not considered, and CSI feedback efficiency is relatively low.